This invention relates to display systems such as a plasma display apparatus used for broadcasting receivers, computer terminals or image displays, light emitting systems such as a rare gas discharge luminescent lamp, a deluxe luminescent lamp using a mixture of blue, green and red phosphors, and phosphors used therein.
Plasma displays applies a process wherein as an excitation source vacuum ultraviolet line which is generated in a negative glow region in minute discharge space containing a rare gas (in the case of using xenon as the rare gas, its resonance line residing in 147 nm) is used and phosphors placed in the discharge space is made to emit light necessary for color display. The structure of this gas discharge cell is disclosed, for example, in xe2x80x9cColor PDP Technology and Materialsxe2x80x9d page 29 (1996, published by C.M.C.).
On the other hand, JP-B 57-352 and JP-B 57-353 disclose that phospho-vanadate phosphors containing rare earth elements as a major component are suitable as phosphors used in display systems such as a plasma display apparatus, and light emitting systems such as a rare gas discharge luminescent lamp, a deluxe luminescent lamp using a mixture of blue, green and red phosphors, etc.
Recently, performance of color plasma displays is improving year by year, but further improvement is still desired. As to phosphors, not only improvement of brightness in the form of powder but also improvement of brightness.in the form of a plasma display panel (hereinafter referred to as xe2x80x9cpanelxe2x80x9d) are essential. In order to improve the brightness of the panel, the control of particle shape is essential. This is because higher density of a phosphor layer directly relates to the improvement of brightness of the panel. Particularly, the rare earth phospho-vanadate phosphors Ln(PcV1xe2x88x92c)O4 [Ln: rare earth element(s)] show a square pillar shape at the composition region showing the maximum brightness, that is, near the molar ratio of P (c) about 0.65. This is very disadvantageous, and improvement is desired.
It is an object of the present invention to provide rare earth phospho-vanadate phosphors overcoming disadvantages of known rare earth phospho-vanadate phosphors, while maintaining high luminescent efficiency of self activated phosphors as a blue phosphor and Eu3+ activated phosphors as a red phosphor even under excitation by not only long wave ultraviolet line (wavelength: 200-400 nm) but also vacuum ultraviolet line (wavelength: 200 nm or less), to provide a display system containing such phosphors, and to provide a light emitting system containing such phosphors.
The present invention provides a rare earth phospho-vanadate phosphor comprising phosphorus oxide and vanadate such as vanadium oxide, said phosphor having a diffraction intensity ratio of the (2, 0, 0) plane to the (1, 1, 2) plane of less than 6.9 in a powder X-ray diffraction pattern.
The present invention also provides a rare earth phospho-vanadate phosphor comprising phosphorus oxide and vanadate such as vanadium oxide, said phosphor being powder particle with an average ratio of long side length to short side length in rectangle of 1.0 to 6.0.
The present invention further provides a rare earth phospho-vanadate phosphor comprising phosphorus oxide and vanadate such as vanadium oxide, and further comprising at least one element in Group IV of the periodic table intentionally added.
The present invention still further provides a display system such as a plasma display apparatus comprising a plasma display panel containing a luminescent layer including as a constituting material the rare earth phospho-vandate phosphor mentioned above.
The present invention also provides a light emitting system such as a rare gas discharge luminescent lamp, a deluxe luminescent lamp using a mixture of blue, green and red phosphors, using the rare earth phospho-vanadate phosphor mentioned above.